A week after a major oil spill in Sept-Îles, Que., crews are still scrambling to clean up kilometres of slick that have spread across the bay.

About 450,000 litres of bunker oil — often used to power ships — spilled from a shipping operation owned by Cliffs Natural Resources overnight on Aug. 31.

'This area is the nursery for the bay.'—Louise Gagnon, Committee for the protection of Sept-Îles Bay

The company said close to 99 per cent of the leaked oil was contained inside a retention dike on site.

The remaining 5,000 litres has since spread across about five kilometres of coastline, according to Environment Quebec.

Emergency crews are racing to clean up the slick before it spreads towards the Maritimes and out to sea by tides, but heavy winds this past week slowed their efforts.

Environment Minister Yves-François Blanchet is expected to visit the site on Sunday and evaluate the damage caused by the spill.

Environmentalists worried about wildlife

Fisheries and Oceans Canada has barred all commercial and recreational fishing in the bay.

The committee for the protection of the Sept-Îles Bay said the area is critical to local wildlife.

"This area is the nursery for the bay. It’s where sediment accumulates and it’s a thriving centre for aquatic life," said committee spokeswoman Louise Gagnon.

There are also concerns about the impact of hydrocarbons contained inside the fuel.

"They are very toxic, often carcinogenic and they will slowly leach out of the oil into the water then they could affect [organisms] in the water," said Subhasis Ghoshal, a McGill civil engineering professor who specializes in contaminated soil and groundwater.

The company behind the spill said it is working on a recovery plan for the affected area.

""This is an unfortunate incident, and Cliffs is committed to taking all appropriate and necessary action to address the issues and remediate the affected area," said Cliffs Natural Resources general manager, Steeve Charest, in a statement.